The present invention relates generally to improved techniques for labeling microtiter plates and the like. More particularly, the invention relates to a high information capacity machine-readable magnetic label formed from magnetic recording wire and embedded in a microtiter plate or the like. Among several aspects, increased resistance to environmental degradation is provided.
Labels are used under many conditions, in many different environments. In particular, chemical laboratories and operations include many objects in which labeling is critical, such as microtiter plates and the like. In many environments in which such plates are employed, chemicals, reagents, solvents and the like may degrade a typical label over time. One example of an object for which labeling is important, and which is commonly used in an environment likely to degrade a typical label, is a microtiter plate used in growing cell cultures for synthesizing and/or screening chemical compounds. A microtiter plate typically contains a number of wells, each well holding a separate sample or culture. The number of wells in a plate may be very large, on the order of tens or hundreds of wells in a single plate. For example, 1536-well plates are increasing in popularity in a number of applications. Each plate therefore holds numerous cultures or samples in its wells, with each culture or sample having a significant amount of work invested. Each plate must be properly identified during each handling step, and a misidentification can cause a plate to be subjected to an incorrect process or environment, or can result in the loss of valuable information about the structures or activities of compounds. It is important, therefore, that a microtiter plate be accurately labeled, since the cost of an inaccurate or misread label can be very high. Moreover, each label must contain sufficient information to uniquely distinguish the plate with which it may be associated. Additionally, as microtiter plates continue to be developed it is possible to add more and more wells to smaller and smaller plates. This potentially increases the information content needed in a label, while simultaneously decreasing the space available for the label. An example of a plate having a large number of wells combined with a relatively small dimension is a 1536-well plate, which is gaining in popularity. These plates have dimensions of approximately 3 inches by 5 inches.
Barcode labels can provide sufficient information density to serve as labels for microtiter plates, but the use of barcode labels encounters certain inherent problems. The simplest way of using a barcode label is to print a paper label and affix it to an object, such as a microtiter plate, through adhesion. However, this is difficult in the case of microtiter plates, as the plates are typically made of the most chemically inert materials available, such as, polypropylene or polystyrene, and these materials typically do not accept adhesives easily. Moreover, in the environment of a chemical laboratory a barcode label suffers from exposure to various reagents and solvents in the environment and is subject to degradation. This is a problem with any label that must be read by visual optical means, as each such label will typically be placed on an outer surface of the labeled object. Such placement allows the label to be contacted by, and degraded by, chemicals in the environment.
Various approaches have been taken to solve the problem of adhesion of a barcode label and of label degradation. These include laser etching of a label onto a plate, embedding of a radio frequency transmitter into the plate, color coding, embedding various fluorescent materials having differing emitting spectral frequencies, and other methods. Methods used to date have been expensive in production of the labeled plates or of the reading equipment, have not yielded sufficient information density in the label, or are insufficiently reliable.
There exists, therefore, a need in the art for a label having a high information capacity, which can be used in a chemical environment without the risk of an unacceptably high level of degradation due to environmental exposure to harsh chemicals and the like, which is reliable, and which is inexpensive to produce and read.
A label according to one aspect of the present invention includes a piece of magnetic recording medium, such as recording wire, embedded within a hollow in a microtiter plate. The recording wire is capable of storing information along its length by maintaining a pattern of sequentially magnetized segments. Information is encoded onto the wire by moving the wire adjacent a fixed recording head or, alternatively, by moving a recording head along the wire. The recording head emits a reversible-polarity field which magnetizes each segment of the wire to a desired polarity, thereby encoding information onto the wire by magnetizing sequential segments of the wire to either a north-south or a south-north polarity. Each magnetized segment has a width not less than the distance between the recording head and the wire. Similarly, the wire is read by moving the wire adjacent a read head or, alternatively, moving a read head along the wire. The sequentially magnetized segments of the wire induce field changes in a field emitted by the read head. The field changes are decoded to extract the information. The label data can be displayed to an operator or an automatic system in order to identify the plate. Alternatively, the label data can be used as an index to information about the plate, in order to allow retrieval of information.
A more complete understanding of the present invention, as well as further features and advantages of the invention, will be apparent from the following Detailed Description and the accompanying drawings.